The ball joint disclosed in Patent Literature 1 has been known as an example of the ball joints of this type. The ball joint disclosed in Patent Literature 1 includes a ball stud including a ball portion formed at a distal end of a shaft member to define a pivot center of a link mechanism, and a holder covering a maximum diameter portion of the ball portion of the ball stud in sliding contact with a spherical surface of the ball portion.
A mechanical element such as a link member is coupled to the shaft member of the ball stud, whereas the holder includes a fixing portion configured to allow another mechanical element to be coupled thereto. Specifically, in many cases, such ball joints are used to couple the two mechanical elements to each other in a freely pivotable manner, and to define a pivot center thereof, thereby constructing link devices such as a parallel link with those mechanical elements.